Smart microgel means a microgel that is stimuli-responsive corresponding to changes of external stimuli (e.g.: temperature, pH, light, ionic strength, electric field or magnetic field, etc.). Depending on the source of raw materials, microgel can be divided into synthetic microgel and natural microgel. Most microgel is prepared from synthetic macromolecules, such as PMA, PVCL, PDEA, PAA, etc. However, such macromolecules have the defects, such as poor biodegradability, poor biocompatibility and certain toxicity. Microgels from natural polymers are more attractive because of their biodegradability, excellent biocompatibility, non-toxicity, and other strengths.
Besides, the research on a temperature sensitive microgel poly(N-isopropylacrylamide) (PNIPAM) is particularly remarkable. Its critical phase transition temperature is 32° C. or so. When the temperature is below its critical phase transition temperature, PNIPAM microgel will be highly swollen, while when the temperature is above its critical phase transition temperature, the microgel will be shrunken, and its swelling degree will suddenly drop. The microgel prepared with PNIPAM has typical temperature sensitivity. People look forward to preparing multifunctional microgel with a variety of stimuli-responsiveness. Therefore, preparing microgel with double sensitivity using the temperature-sensitive material PNIPAM in combination with the environmental sensitivity of other intelligent materials becomes a research hotspot. But at present, there is no report on microgel with multiple sensitivity based on natural macromolecules.